Understand what you are saying. I suppose you felt that Chelsea win was a little serendipitous. I just felt that the game as a whole, Chelsea responded with more options than us during difficult periods. We lacked that bit of option with pace in attack.
We lost games due to our lack of pace in defence, no doubt. But my point in discussion is more on the Alli, Eriksen combo, compared with the groups other top teams have. What we had achieved last season (as mentioned in your well written paragraph on how we performed against top teams) has been nothing short of remarkable. But if we are to be critical (which we have to be if we are talking about challenging for the title)I am in the opinion that Alli and Eriksen are not without weaknesses and still not the best compared to others.
It is easy to say we lost to Chelsea (both the title and FA cup) due to our defence. However we can also say we didn't score enough when matters. You can can we had scored so many thru out the season, but we conceded little too. My point as I said, is more about Alli and Eriksen compared to others, not about our entire team.
I am glad you agreed we should sign players with pace. As you might disagree, I am also in the opinion that had we have Mahrez last season, we might be better off. He could have offered something different to Alli and Eriksen, when things get a little predictable.